SSF - I decided to switch to Series instead of Parallel

[MAWilsonPE]

Hello Solar Fans!

I have the 1200 watt Super Solar Flex factory system. I have disconnected the Jaboni MPPT Controllers in favor of the Victron 100/50 MPPT Controllers. The factory setup has two 300 watt panels wired in parallel to each of two Jaboni controllers. The Jaboni controllers are rated for a max PV voltage input of 45VDC and a max PV amperage of 30A netting a maximum power capability of 550 watts. With 600 watts of panels on each one, these are underrated.

The Victron 100/50 controllers can handle up to 100 VDC of PV input voltage. They do not provide a max PV amperage but state that the maximum to your batteries is 50 amps, for Lithium at 13.5 volts that is 675 watts.

The 300 watt Jaboni solar panels are rated to provide 32VDC at maximum power and 9.3 amps. Two of these wired in parallel will feed 32VDC and 18.6 amps to the controller.

I found an online PV voltage drop calculator here:
https://photovoltaic-software.com/so...lculator-dc-ac

I estimate the run of 10AWG solar cable from the panels to the controller to be about 30-35 feet so I used 10 meters. Using that calculator and 32VDC, 18.6 amps, copper 2.5mm wire (10awg), 25 degC, a 10 meter one way run, the calculated voltage drop is 2.6 volts or about 8% (48 watts). I read that the voltage drop should always be less than 3% in a DC system.

Re-wiring the panels from parallel to series is very simple, took less than five minutes and I could even use the existing cables. (Don't do this in sunlight when the panels are making power, cover them or wait until dusk when the output is <10 watts). You remove the 2-way splitters, plug the (+) from one panel into the roof connection, plug the (-) from that panel to the (+) of the second panel, and the (-) from the second panel into the roof connector.

Connecting two panels in series doubles the voltage and halves the amperage compared to a parallel setup. Running the calculator again using 64 volts, 9.3 amps, everything else the same, results in a voltage drop of only 1.3 volts, or 2% (12 watts).

So it would seem i can pick 6% more efficiency or about 36 watts with this simple change. What do you think, am I missing anything?

Thanks, Mike

[MAWilsonPE]

Well it looks like this may have made a difference as predicted. See the screen shot below. I had seen a Pmax of 610 watts previously with the panels wired in parallel. Now, with them wired in series, I have achieved a Pmax of 650 watts (from two “300 watt” panels)!! Woohoo!!

Best Mike